A panel of alloreactive T cell clones derived from a single donor has been established and characterized for its fine specificity patterns. It has thus been possible to assign each of the clones to one of four fine specificity groups. In order to attempt to correlate fine specificity with receptor gene utilization, the TcR alpha and beta variable gene segments used by these clones are being analyzed. An alpha variable gene derived from a member of the most common group is being isolated from a restricted cDNA library. Its representation in the other members of the panel will be assessed.